This invention relates generally to the field of telecommunications, and more particularly to a method and system for providing broadcast channels over an emulated subnetwork on a UPSR SONET ring.
Telecommunications systems include customer premise equipment (CPE), local loops connecting each customer premises to a central office or other node, the nodes providing switching and signaling for the system, and internode trunks connecting the various nodes. The customer premise equipment (CPE) includes telephones, modems for communicating data over phone lines, and computer and other devices that can directly communicate video, audio, and other data over a data link. The network nodes include traditional circuit-switched nodes that have transmission paths dedicated to specific users for the duration of a call and employ continuous, fixed-bandwidth transmission and packet-switch nodes that allow dynamic bandwidths, dependent on the application. The transmission media between nodes may be wireline or wireless.
One type of wireline transmission media is optical fiber which is a thin strand of glass that is designed to carry information using pulses of light. Separate optical fibers are bundled together and encased in an outer sheath to form fiber cables. Optical fiber provides users with higher reliability, superior performance, and greater flexibility than traditional copper-based systems.
Optical transmission facilities are installed in the form of synchronous optical network (SONET) rings. SONET defines a line rate hierarchy and frame format as described by the American National Standards Institute (ANSI) T1.105 and T1.106 specifications. SONET rings are typically bidirectional to provide redundant transmission paths and protection in case of a network failure. Nodes on a SONET ring provide add-drop multiplexing and digital cross-connect functionality for traffic on the ring.
The simple network management protocol (SNMP) is heavily used for network management in the data communications industry. SNMP uses User Datagram Protocol (UDP) and Internet Protocol (IP) packets to communicate management information between a management station and a network node, which is not readily transportable on a SONET ring. As a result, SONET nodes cannot be remotely managed using SNMP and other protocol using IP and similar messaging because the network management stations do not have the ability to communicate with nodes beyond an immediately connected node. Thus, the network management station has no knowledge of the existence of any other nodes on the SONET ring outside the immediate node. To communicate with multiple nodes on the SONET ring, additional management network external to the ring must be used which is costly to implement and maintain.
The present invention provides an improved method and system for providing a broadcast channel over an emulated subnetwork. In particular, Internet Protocol (IP) or other suitable traffic is transmitted in virtual channels of an asynchronous transfer mode (ATM) subnetwork on a synchronous optical network (SONET) ring. Accordingly, simple network management protocol (SNMP) and other suitable types of management and control traffic can be broadcast from and to remote resources on a SONET ring.
In accordance with one embodiment of the present invention, a method and system for communicating traffic on an emulated subnetwork of a telecommunications ring having a plurality of nodes interconnected by a transmission media includes obtaining traffic at a node on the telecommunications ring. The traffic may be generated within the node or received from an external device on a local area or other network. The traffic is segmented into a plurality of discrete segments. A set of broadcast cells is generated by adding an address header to each segment. The address header identifies a virtual channel dedicated to the node for broadcast traffic in the subnetwork on the telecommunications ring. The set of broadcast cells are transmitted in the virtual channel of the subnetwork and within a frame of the telecommunications ring. In response to receiving the set of broadcast cells in the virtual channel, each remaining node on the telecommunications ring both retransmits and processes the broadcast cells.
More specifically, in accordance with a particular embodiment of the present invention, the telecommunications ring is a synchronous optical network (SONET) ring. In this embodiment, the broadcast cells comprise asynchronous transport mode (ATM) cells each including an ATM header identifying the virtual channel. The ATM cells may be formed by segmenting broadcast traffic in the form of an Internet protocol (IP) packet to form AAL5 cells and adding the ATM header to the cells to form the ATM cells.
Technical advantages of the present invention include providing an improved management system and method for a SONET or other suitable type of telecommunications ring. In particular, management, control, and similar types of information are transmitted by each node in an ATM subnetwork on the SONET ring. Each node can act as a gateway to transmit and receive management and control messages between a network management station and a remote management agent connected to another node on the SONET ring. Accordingly, a centralized management station may use simple network management protocol (SNMP) and other conventional and readily available protocols to manage remote nodes. External management networks may be eliminated. This improves manageability of a SONET ring and reduces cost.
Another technical advantage of the present invention includes providing dedicated broadcast channels in a SONET ring. In particular, an ATM virtual channel is assigned to each node in the SONET ring. Each node, in response to receiving traffic in a virtual channel of another node on the ring, both processes and retransmits the traffic. In addition, each virtual channel is bidirectional and thus protected against a network failure.
Still another technical advantage of the present invention includes providing ring frame encapsulation for management messages broadcast on the SONET ring. The ring frame identifies the source node and the destination node of the traffic, as well as the message type. Provision of the ring frame allows each node receiving the message to efficiently process the message and determine whether it is destined for that node and thus in need of further processing. Accordingly, each node can efficiently process broadcast traffic within the SONET ring.
Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, description, and claims.